Batch processing in the United States represents a huge industry segment. Batch processing involves producing fixed quantities (batches) of product by combining ingredients and treatments according to defined sequences of steps called “recipes” or “production recipes.” Presently, five percent of the United States gross national product is based on industries that rely on batch manufacturing (including chemical, food and beverage, and pharmaceutical industries).
Recipes define how to make a company's products, whether the company is manufacturing specialty chemicals, food and beverages, pharmaceuticals, or consumer goods for example. Today, batch processing often involves using the same recipe for the same product, even under varying process conditions. Because recipes are costly to develop and difficult to tailor for varying processing conditions or production requirements, successful recipes are reused repeatedly in fixed form and for fixed batch sizes, even when this results in undesirable batch-to-batch quality variations and larger inventories than necessary. Even when the batch can accommodate a different—and economically more viable—recipe, the effort and uncertainty involved in modifying the current recipe is considered too risky or too time-consuming to attempt. It is risky because the scientific and engineering knowledge required to modify the recipe is complex and is not available as part of the recipe. In fact, this knowledge is often lost as recipes make the transition from laboratory to pilot plant to production plant. For example, a recipe instruction such as “Control heat rate to <2° C./min” may have been determined from complex scientific reasoning such as: “Control heat rate to limit the gas evolution to less than 1 L/min because higher gas evolution rates can cause cracking of the treated product, especially if the raw material contains moisture.” Today, however, this complex instruction is reduced to a simple one, to cover all situations.
The recipes used in batch manufacturing today are merely a set of instructions that do not include the scientific or engineering knowledge that is the basis for these actions. Because the underlying knowledge (for example, heat rate is a function of gas evolution rate and initial moisture content; gas evolution rate is described by first order kinetics) and desired state (for example, no cracking, moisture content less than 0.01%), is not included, and often lost, making changes to the recipes is usually a trial-and-error operation.
Today, recipes are generally not modified. Recipes are initially developed and implemented for a specific batch size. Scaling up a recipe from a pilot to production is a challenging and time-consuming task. Once the recipe is proven in production runs, it is difficult to change the quantity of material produced. Furthermore, many recipes, especially those involving chemical reactions, do not scale linearly.
However, using a fixed recipe for all batches leads to products of inconsistent quality. Batch processing is a complex activity where variability in processing conditions is almost certain and the ability to modify a recipe is desirable. Therefore, there is a need to tailor a recipe for the varying processing conditions and production requirements for a specific batch.